1. Field of the Invention
This invention pertains to mineral freight trains employing gondola or hopper type freight cars and to apparatus and methods for unloading the cargo of the train in a efficient manner.
2. Description of the Prior Art
In the present era, where railroads are exposed more and more to financial difficulty, it becomes more and more important for efficient and relatively inexpensive techniques to unload bulk materials from trains of hopper or gondola cars. More particularly it has been determined by railroads that the use of unit trains for the hauling of bulk material, such as minerals, a prominent example of which are coal trains for supplying coal as fuel for electrical power plants, are necessary in order to reduce the transportation cost of such materials and to make coal a valuable competitive fuel when contrasted with other fuels. Large trains of one hundred or more hopper cars are filled at a mine and move directly as a unit to an electrical power station or to a central dumping point for a number of power stations where the contents of such trains are dumped. The trains then return to the mine for reloading.
For certain materials which flow readily when shipped in bulk, such as grain, the hopper cars may be provided with movable bottom platforms such that the bulk material flows from the car through the bottom thereof. Where coal is involved, it will be noted that the same frequently is exposed to water during the mining, processing or transportation thereof and when the water freezes, the coal normally solidifies so that it does not flow, but must be removed from the cars as one or more large bulky pieces. Present devices actually employed for dumping unit trains comprise power rotating devices for the cars which require each car to be separately decoupled from the train, rotated 180.degree. so that its contents is dumped, returning the car to the normal upstanding position and recoupled to the train. This is obviously a time consuming procedure involving manual operations which increases substantially the transportation cost of the material. Other systems which form a part of the prior art, but which have not, to the knowledge of the applicant, been used or tried, include loop systems of the type illustrated in U.S. Pat. No. 216,736 to Ramseur (1906), Stillwell et al U.S. Pat. No. 2,540,766 (1951), Stehli U.S. Pat. No. 1,027,084 (1912) and Haubner U.S. Pat. No. 1,612,316 (1926). Each of these patents is directed to the passing of a number of cars or containers through a loop, however in each event, the open end of the car does not face the center or axis of the loop but faces the opposite direction. These arrangements are not feasible with todays hopper or gondola car constructions inasmuch as the wheel carriages of present gondola cars are secured to the main open section of the cars such that if the car is inverted while the weight of the car is supported solely by the carriage, the cars will separate from the carriage. In order to pass a car through a loop with the open end of the car facing outwardly of the loop and with the weight of the car being supported when the car is inverted by the wheels, it will be necessary to modify substantially todays presently available cars in order to improve the connection between the carriages and the bodies of the cars. This problem may also be seen in the system of O'Toole U.S. Pat. No. 1,491,060 (1924). Other train and unloading arrangements forming upon the prior art include Bell U.S. Pat. No. 2,763,382 (1956) which is directed to a continuous car dumping arrangement but which requires in addition to special track arrangements, special flat car clamping devices which receive the gondola cars and clamp the same in position while passing them through a side inversion in order to move their contents. The Pardee U.S. Pat. No. 2,121,365 (1938) provides for a side ways rotation of the cars to move their contents and provides for guide means formed on the side of the cars to support the weight of the car and prevent the separation of the car from the wheel carriage during the unloading operation. The provision of the side guide means and support means of Pardee requires a formation of a car dumping arrangement having substantially close tolerances to accommodate the guide means and further requires a substantial modification to each of the cars. More paticularly, in the event of a distortion of the shape of the car, which frequently occurs during normal car usage over a long time period, the car will become stuck while passing through the Pardee arrangement. Frequent shutdown of the Pardee dumping arrangement to remove "distorted" hopper cars will result.
Unloading arrangement for other commodities such as the removal of pears and cherries from a number of cartons or containers as illustrated in Turner U.S. Pat. No. 1,945,758 (1934) comprises a substantially different problem than the removal of the contents of a one hundred car train where each car weighs 65,000 pounds and contains a 200,000 pound load.